1. Field of the Invention
The present invention relates to ammunition rounds in which propellant charge is located in two separate cartridges.
2. Discussion of Prior Art
A primary role for the main battle tank is to take and hold ground. To achieve this it has to have the capability of defeating enemy armour. In recent times there have been substantial improvements in the effectiveness of armour arrays, and to counter these improvements and ensure that the main battle tank retains that capability corresponding improvements are required in the performance of solid propellant tank gun/ammunition systems. These improvements have been achieved mainly by a combination of significant increases in propellant charge weight and the use of very long penetrators so as to deliver the increased kinetic energy per unit area necessary to defeat advanced armour arrays. Because of a number of factors, primarily the requirement to ensure that any new system is compatible with modified existing main battle tank designs, constraints are placed on the maximum diameter for the ammunition round and thus, to accommodate the increased propellant, total round lengths must increase.
In order to facilitate handling of such rounds and stowage within a vehicle it is a requirement, in some cases, to split the ammunition round into two parts. All modern systems use cartridge cases which are either fully or partly combustible and these have to survive a certain amount of rough handling and may occasionally get wet or be exposed to moisture. In order to ensure that the propellant and the pyrotechnic elements contained within the two cartridges are sufficiently protected it is necessary to design robust and water resistant cartridge cases.
Generally the ballistician strives to devise systems which will achieve a smooth, uninterrupted ignition of all of the propellant contained in the gun chamber. In a two part system, where the sole means of propellant ignition is contained in the rear of the primary cartridge, the introduction of thick walled combustible caps, which separate the two propellant charges, delays the ignition of the propellant in the secondary cartridge and this can result in the formation of pressure waves which in extreme cases can increase to a magnitude capable of damaging the gun or projectile. The latter case could result in the detonation of an explosive projectile whilst still within the bore. However, the use of a less substantial barrier to mitigate this problem leaves the cartridge more vulnerable to damp and to damage during handling.